Error 500 when creating a new topic/message if User name contains non-latin letters

1. Sign up the user with non-latin letters in user name (for ex, "КаZантип")
2. Sign in.
3. Create any topic.
As a result, 500 error has been shown.
5. Select any topic.
6. Press "Answer" button
As a result, 500 error has been shown.